1. Field of the Invention
The present invention generally relates to the dissipation of operating heat from portable computers and, in a preferred embodiment thereof, more particularly relates to apparatus for transferring heat generated within the base housing of a portable computer to its lid housing for dissipation to ambient.
2. Description of Related Art
As portable computers become more sophisticated and powerful, being provided with faster and more densely packed electronic components in their interiors, the effective dissipation of operating heat from the computer becomes an increasingly critical design task. In a typical construction thereof the popular "notebook" portable computer includes a base housing in which the main heat generating electronic components such as a processor, hard, floppy and CD ROM drives and the like are disposed, and a display screen housing pivotally secured to a rear top side edge portion of the base housing.
In early versions of the notebook computer the base housing operating heat was simply allowed to transfer outwardly to the base housing exterior surface for dissipation to ambient. However, as the operating heat loads increased it became more difficult to maintain the exterior surface temperature of the base housing at an acceptable temperature. Thus, more exotic and correspondingly more expensive heat dissipation techniques, such as internal cooling fans and heat sinks within the base housing were employed.
A recent approach to this increasing operating heat dissipation problem in notebook computers has been to transfer at least some of the operating heat generated in the base housing to the display screen housing for dissipation to ambient. The two primary design challenges presented in attempting to transfer base housing heat to the display housing are (1) the potential problem of creating undesirable temperature rises in portions of the display housing, and (2) the necessity of transferring heat through the hinge area that pivotally couples the base and display housings.
A proposed solution to these problems is illustrated and described in copending U.S. application Ser. No. 08/769,795 filed on Dec. 19, 1996, now U.S. Pat. No. 5,781,409 and assigned to the same assignee as the present application. Shown in such copending application is a base-to-display housing operating heat transfer system utilizing a first heat pipe disposed in the base housing, a second heat pipe disposed in the display housing, and a copper hinge block disposed in the display housing.
An evaporating end portion of the first heat pipe is in thermal communication with a heat generating component within the base housing, and a condensing end portion of the first heat pipe is rotatably received within the hinge block and lubricated therein with thermal grease. Thus, when the display housing is pivoted relative to the base housing, the hinge block is rotated about the condensing end of the first heat pipe. An evaporating end portion of the second heat pipe is fixedly secured within the hinge block, and a condensing end portion of the second heat pipe is in thermal communication with the back wall of the display housing.
Operating heat from the heat generating component within the base housing is thus sequentially transferred through the first heat pipe to the hinge block, from the hinge block to the second heat pipe, and through the second heat pipe to the display housing back wall for dissipation therefrom to ambient.
While this previously proposed method of transferring operating heat from the base housing of a portable computer to its display housing for dissipation therefrom to ambient desirably results in lowered base housing exterior surface temperatures during operation of the associated computer, it carries with it certain limitations and disadvantages.
For example, extra weight is added to the overall computer by the copper hinge block; surface degradation from the frictional wear between the first heat pipe condensing end portion and the hinge block can lead to a reduction in heat transfer interface reliability at this portion of the heat transfer system; repeated flexing of the condensing end portion of the first heat pipe at the entrance to the hinge block can potentially fatigue the first heat pipe; and a relatively high heat transfer structure cost is presented by the requirement for two heat pipes and the copper hinge block structure.
In view of this it can be readily seen that a need exists for improved apparatus for transferring base housing operating heat to the display or lid housing of a portable computer. It is to this need that the present invention is directed.